Trace element abundances in basalts of Nauru Basin

Batiza, Rodey; Larson, Roger L.; Schlanger, Seymour O.; Shcheka, S. A.; Tokuyama, Hidekazu

doi:10.1038/286476a0

Cited by 17 publications

(4 citation statements)

References 20 publications

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“…tillo et al, and Schlanger and Moberly, this volume, for discussions of age of the basalts). Chemically and mineralogically, the basalts are not unlike some types of mid-ocean ridge basalts (MORB), with LIL-element patterns generally depleted relative to chondrites, and low SR isotope ratios, but they are sufficiently different in a number of respects to set them apart (Batiza et al, 1980;; Tokuyama and Fujii et al, 1981;Saunders, and Castillo et al, this volume). The sheet-flows form a voluminous, chemically distinctive form of submarine intraplate volcanism, generated on preexisting ocean crust and derived from different parent magmas (and/or sources) from MORB. This chapter describes the petrography and geochemistry of 75 basalt samples collected during Leg 89 (Table 1) from the deepest part of the sill-flow complex at Hole 462A, between 1072 and 1209 m sub-bottom depth.…”

Section: /G E Australiamentioning

confidence: 99%

Petrology and Geochemistry of Oceanic Intraplate Sheet-Flow Basalts, Nauru Basin, Deep Sea Drilling Project Leg 89

Floyd¹

1986

Initial Reports of the Deep Sea Drilling Project

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Reentry of Hole 462A during Leg 89 resulted in the penetration of a further 140 m of basalt sheet-flows similar to those found during Leg 61 at the same site. Twelve volcanic units (45 to 56) were recognized, comprising a series of rapidly extruded, interlayered aphyric and poorly clinopyroxene-plagioclase-olivine phyric, nonvesicular basalts. All exhibit variable, mild hydration and oxidation, relative to fresh oceanic basalts, produced under reducing, low-CO 2-activity conditions within the zeolite facies. Secondary assemblages are dominated by smectites, zeolites, and pyrite, produced by low-temperature reaction with poorly oxygenated seawater. No systematic mineralogical or chemical changes are observed with depth, although thin quenched units and more massive hypocrystalline units exhibit slightly different alteration parageneses. Chemically, the basalts are olivine-and quartz-normative tholeiites, characterized by low incompatible-element abundances, similar to mildly enriched MORB (approaching T-type), with moderate, chrondite-normalized, large-ionlithophile-element depletion patterns and generally lower or near-chrondritic ratios for many low-distribution-coefficient (K D) element pairs. In general, relative to cyclic MORB chemical variation, they are uniform throughout, although 3 chemical megagroups and 22 subgroups are recognized. It is considered that the megagroups represent separate low-pressure-fractionated systems (olivine + Plagioclase ± clinopyroxene), whereas minor variations within them (subgroups) indicate magma mixing and generation of near-steady-state conditions. Overall, relatively minor fractionation coupled with magma mixing produced a series of compositionally uniform lavas. Parental melts were produced by similar degrees of partial melting, although the source may have varied slightly in LIL-element content.

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Section: /G E Australiamentioning

confidence: 99%

Petrology and Geochemistry of Oceanic Intraplate Sheet-Flow Basalts, Nauru Basin, Deep Sea Drilling Project Leg 89

Floyd¹

1986

Initial Reports of the Deep Sea Drilling Project

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“…The sheet-flows cover extensive areas of the west and central Pacific Ocean (Winterer, 1973), and are the products of fissure eruptions through thermally domed Jurassic ocean floor (Larson and Schlanger, 1981;Schlanger and Premoli Silva, 1981). The sheet-flow basalts have incompatible-element-depleted compositions similar to those of mid-ocean ridge basalts (MORB), but differ significantly in some aspects of this chemistry (Batiza et al, 1980;Saunders, this volume;Floyd, this volume). Cretaceous volcaniclastic sediments are also abundant throughout basinal deeps of the western Pacific, and represent mass-flow accumulations of hyaloclastite debris derived from the flanks of adjacent seamounts.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of Primary and Secondary Phases in Intraplate Basalts and Volcaniclastic Sediments, Deep Sea Drilling Project Leg 89

Floyd¹,

Rowbotham²

1986

Initial Reports of the Deep Sea Drilling Project

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Electron microprobe data are presented for clinopyroxenes, plagioclases, palagonites, smectites, celadonites, and zeolites in Hole 462A sheet-flow basalts and Site 585 volcaniclastic sediments. Glomerocrystic clinopyroxenes in Hole 462A are predominantly Ti-poor augites with minor fractionation to ferroaugites in rim portions. Quenched plumose clinopyroxenes show considerable variation from Ca-rich to Ca-poor augites, although all are characterized by being Tirich and Cr-poor relative to the glomerocrysts. Two differentiated series of Site 585 pyroxene compositions, calcic augite and diopside-salite, demonstrate the coexistence, in the vitric and lithic clasts, of tholeiitic and alkali basalt types, respectively. Plagioclase compositions in all samples are mainly labradorites, although some zoned Hole 462A glomerocrysts range from An 73 to An 20 and are characterized by high Mg and Fe contents in the more calcic varieties. The K content of the plagioclases is highest in the more sodic crystals, although the overall higher orthoclase component of Site 585 plagioclases reflects the generally higher bulk-rock K content. The compositions of both secondary smectites and celadonites are similar irrespective of the alteration location (glass, matrix, vesicles, etc.), although brown smectites replacing interstitial glass have marginally higher total Fe contents than pale green and yellow smectites. Analyzed zeolites are mainly phillipsites with variable alkali content, and, together with associated celadonite, represent late-stage alteration repositories for K under mildly oxidizing conditions. The compositions of both early and late secondary minerals are typical of those formed by the submarine alteration of basaltic rocks at low temperatures.

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“…These submarine provinces are generally considered to represent episodes of crustal thickening soon after or as a continuation of axial activity (Saunders, 1986;Mahoney, 1987) generated above the inflated heads of large mantle plumes during the early Cretaceous (Richards et al, 1989). The tholeiitic basalts of the oceanic plateaus have a broad MORB-like geochemistry, although they exhibit a number of distinctive features that set them apart (Batiza et al, 1980;Floyd, 1989). In particular they are enriched in LIL elements, are characterized by generally flat (or less depleted) REE patterns and have different incompatible element ratios, in particular lower Zr/Nb, Zr/Ta, La/Ta, and Hf/Th, relative to normal-type mid-ocean ridge basalt (N-MORB).…”

Section: Tholeiitic Basalt Lavasmentioning

confidence: 99%

Geochemistry and Petrography of Cretaceous Sills and Lava Flows, Sites 800 and 802

Floyd¹,

Winchester²,

Castillo³

1992

Proceedings of the Ocean Drilling Program

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On the basis of their respective eruptive environments and chemical characteristics, alkalic dolerite sills from the northern Pigafetta Basin (Site 800) and tholeiitic pillow lavas from the Mariana Basin (Site 802) sampled during Ocean Drilling Program Leg 129 are considered to represent examples of the widespread mid-Cretaceous volcanic event in the western Pacific. Both groups of basic rocks feature mild, low-grade, anoxic smectite-celadonite-carbonate-pyrite alteration; late-stage oxidation is very limited in extent, with the exception of the uppermost sill unit at Site 800. The aphyric and nonvesicular Site 800 alkalic dolerite sills are all well-evolved mineralogically and chemically, being mainly of hawaiite composition, and are similar to ocean island basalts. They are characterized by high contents of incompatible elements (for example, 300-400 ppm Zr), well-fractionated rare earth element patterns ([La/Yb] N 18-21) and HIMU isotopic characters. They probably represent deep-sea, lateral, intrusive off-shoots from nearby seamounts of similar age. The olivine-plagioclase ± clinopyroxene phyric tholeiitic pillow lavas and thin flows of Site 802 are nonvesicular and quench-textured throughout. Relative to normal-type mid-ocean ridge basalt, they are enriched in large-ion-lithophile elements, exhibit flat (unfractionated) rare earth element patterns and have distinctive (lower) Zr/Nb, Zr/Ta, La/Ta, and Hf/Th ratios. Overall they are compositionally and isotopically similar to the mid-Cretaceous tholeiites of the Nauru basin and the Ontong-Java and Manihiki plateaus. The Site 802 tholeiites differ from the thickened crustal segments of the oceanic plateaus, however, in apparently representing only a thin veneer over the local basement in an off-axis environment.

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Trace element abundances in basalts of Nauru Basin

Cited by 17 publications

References 20 publications

Petrology and Geochemistry of Oceanic Intraplate Sheet-Flow Basalts, Nauru Basin, Deep Sea Drilling Project Leg 89

Petrology and Geochemistry of Oceanic Intraplate Sheet-Flow Basalts, Nauru Basin, Deep Sea Drilling Project Leg 89

Chemistry of Primary and Secondary Phases in Intraplate Basalts and Volcaniclastic Sediments, Deep Sea Drilling Project Leg 89

Geochemistry and Petrography of Cretaceous Sills and Lava Flows, Sites 800 and 802

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